Today, a variety of wireless networking technologies support network connectivity. Wireless wide area network (WWAN) technologies, such as those embodying the GPRS, WCDMA, 802.16, etc. protocols, enable computing devices to connect to remote computer networks via cellular data transmission networks. Wireless local area network (WLAN) technologies, such as those incorporating the IEEE 802.11 a/b/g, HomeRF, Hiperlan/2, etc. protocols enable users to access local area network resources via wireless access points/transceivers. Wireless personal area network (WPAN) technologies, such as Ultra Wideband (UWB), and Bluetooth (BT), represent yet another wireless technology incorporated within computers today. There are other technologies that fall in the realm of command and control and inventory control such as Zigbee and RFID respectively. Physical and media access layer components associated with these technologies, in many instances, operate within overlapping frequency ranges in an uncoordinated manner—which results in signal interference.
Depending upon configuration and proximity to wireless network transceivers, a computing device receives/transmits radio frequency waves associated with one or more of the above-identified wireless technologies. In fact, depending upon the location, a computing device is able to maintain simultaneous wireless network connections via distinct network interface cards (NICs) installed on the computing device. Simultaneous availability/existence of wireless communication technologies and their associated wireless signal transmissions arise, for example, within an office environment that supports wireless local area network, wireless wide area network, and personal area network connectivity. The presence of multiple simultaneous networking technology options enhances flexibility with regard to how a computing device connects to networks and/or resources (including computer peripherals such as speakers, a keyboard, a mouse, etc.).
However, the abundance and wide variety of RF sources also increases the likelihood that a computing device having wireless communication capabilities will encounter and/or create signal interference, which leads to lowered quality of service and an unpleasant user experience. There are many types of interference—each having differing characteristics. For example, two wireless transceivers that utilize overlapping frequency spectrums create signal interference resulting in lost packets, dropped connections and uneven throughput (in the case of streaming connections). In some instances, a first transceiver operates at a sufficiently high signal power such that its operation is not affected by other competing signals; however, the operation of a second, lower power wireless transceiver is saturated by the higher power interfering signal from the first transceiver.
Interference can arise from differing sources. A first type of interference arises from the computing device itself that is simultaneously operating more than one wireless transmitter/receiver. For example, a computing device supports multiple wireless interfaces, incorporating different wireless technologies, that use overlapping wireless signal frequency bands. As a result, the wireless interfaces create conflict when used simultaneously. An example of such overlapping wireless technologies involves using IEEE 802.11b or 802.11g simultaneously with Bluetooth PAN appliances—since 802.11b/g transceivers utilize wireless frequencies that overlap frequencies potentially utilized by a Bluetooth wireless connection.
In an exemplary scenario where the existence of simultaneously active wireless interfaces/transceivers on a single computing device leads to signal interference, a DVD player streams a movie over an 802.11b WLAN connection to a personal computer. The personal computer user is simultaneously using a wireless (Bluetooth) mouse to check on movies facts in a separate window that is downloading pages from the Internet (accessed through a Bluetooth phone connected over GPRS). The Bluetooth signal between the mouse and the personal computer and between the personal computer and the Bluetooth phone conflicts with audiovisual data streaming signal from the DVD to the personal computer. The signal interference results in jerky presentation of the movie. The mouse movements are also likely to be jerky.
In another exemplary interference scenario, a camcorder sends an audiovisual stream to a personal computer over ultra wideband (UWB). At the same time, a user is connected to a wireless transceiver (access point) for a network over an 802.11a wireless connection that connects the user to the Internet via a cable modem/DSL line. In this potential interference scenario, the 802.11a signal interferes with the UWB data transmissions. As a consequence, the streamed recorded session appears jerky.
A second type of interference source arises from signal transmissions to/from other computing devices or interference sources that exist/operate independently of a computing device experiencing signal interference with regard to one or more wireless transmitters/receivers—external interference sources over which the computing device has no control. In addition to other computers, access points, etc. such interference can also arise from a variety of external interference sources such as cordless telephones, microwave ovens, etc.
A number of signal collision avoidance schemes operate within a single wireless protocol/technology. For example, in the area of wireless WAN, transceivers/drivers utilize CDMA, TDMA, and FDMA protocols that avoid transmission collisions with other transmitters utilizing the same technology. Such collision avoidance schemes are not well suited for heterogeneous wireless transmissions over shared frequency ranges because the different wireless transmissions can be using different collision avoidance protocols. This is especially true in the case of WPAN/WLAN wireless transceivers such as Bluetooth/UWB and 802.11 competing simultaneously for transmission time within unlicensed/unregulated overlapping frequency ranges.
One way for computing devices to respond to encountering signal interference is to allow the affected connection to degrade/fail. The computing device becomes aware of a particular connection failing. If the connection fails, the user is prompted to try re-connecting, or the user potentially selects an alternative network communication media (e.g., a wired connection to a network), or the computing device does this automatically if so prescribed by policy.
Known MAC drivers have implemented conflict avoidance schemes handling two wireless technologies. Vendors have implemented collaborative and/or signal cancellation schemes to avoid interference. For instance, in a single system including both an 802.11b and a Bluetooth transceiver, the system coordinates transmissions at the MAC level through a mode switch. The mode switch operation is based upon lower-layer procedures such as beacon reception (for 802.11b), paging (for Bluetooth), or by interleaving packets. The vendor's NIC can potentially support both Bluetooth (BT) and 802.11 in which case the NIC can determine when either of the two competing/interfering technologies is being used and stops the other transmission until the first is done. If there are two NICs, one for Bluetooth and one for 802.11, the two NICs could potentially be hardwired to each other so that one can determine when the other is transmitting and stop its own transmissions. This is a two-wire or four-wire approach depending upon the number of wires between the two NICs. Alternatively, a notification about a transmission can potentially be provided by one driver to another, for instance the Bluetooth driver or the 802.11 driver potentially provides a callable interface that would be used by the other driver to provide notification of a transmission. The mode switch arbitrates between 802.11b Bluetooth traffic. Then the switch allows transmission in favor of the traffic with higher priority. It is common to let traffic from HID devices (keyboard and mouse) to have the highest priority. Otherwise, 802.11b will have the priority traffic.
Furthermore, known wireless network interface selection criteria base automated selection of a Wi-Fi technology upon SSID (identity of a wireless network—facilitating determination of connectivity to particular resources such as the Internet) and maximum supported network connection speed. Under this relatively simple arrangement, if two differing wireless technologies offer connectivity to a same network/resource, then the faster wireless technology is selected.